The STL provides the function std::this_thread::sleep(), which supports very fine-grained (nanosecond-granularity) sleeps on non-Windows platforms. On Windows, however, it is implemented (in both Microsoft's STL and in libc++) using the Win32 Sleep() API, which is millisecond granularity. It's also not very punctual as sleep APIs go.
On Windows 10 build 17134 or later, the CreateWaitableTimerEx() API got support for a new CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag, which allows setting timers with sub-millisecond granularity. Sleep can be implemented using this API.
I've implemented a couple of simple std::this_thread::sleep() alternatives which are more disciplined about their behavior:
- timers::deadline_sleep - Attempts to sleep exactly the requested duration. To accomplish this, it uses an "adaptive sleep" mechanism, where it sleeps for as long as it feels it can without overshooting the deadline, and then spin-waits for the rest of the duration.
- timers::precise_sleep - Attempts to sleep using the highest-precision sleep API available on the OS. For Windows, this means either a high resolution waitable timer or plain old Sleep().
The main() function in this program will run through some exercises of various sleep durations and measure how precise the actual sleep duration was.
Here's a run on Windows 11 (22621.1848):
Windows timer resolution minimum 15625 us, maximum 500 us, current 500 us
Windows timer resolution set to 500 us
wait time: 50000 us
std::this_thread::sleep_for
elapsed: 50379 us, error: 379 us (0.76%)
elapsed: 50469 us, error: 469 us (0.94%)
elapsed: 50024 us, error: 24 us (0.05%)
elapsed: 50508 us, error: 508 us (1.02%)
elapsed: 50023 us, error: 23 us (0.05%)
timers::precise_sleep::sleep_for
elapsed: 50163 us, error: 163 us (0.33%)
elapsed: 50020 us, error: 20 us (0.04%)
elapsed: 50527 us, error: 527 us (1.05%)
elapsed: 50373 us, error: 373 us (0.75%)
elapsed: 50434 us, error: 434 us (0.87%)
timers::deadline_sleep::sleep_for
elapsed: 50002 us, error: 2 us (0.00%)
elapsed: 50002 us, error: 2 us (0.00%)
elapsed: 50001 us, error: 1 us (0.00%)
elapsed: 50002 us, error: 2 us (0.00%)
elapsed: 50002 us, error: 2 us (0.00%)
wait time: 20000 us
std::this_thread::sleep_for
elapsed: 20127 us, error: 127 us (0.64%)
elapsed: 20014 us, error: 14 us (0.07%)
elapsed: 20506 us, error: 506 us (2.53%)
elapsed: 20482 us, error: 482 us (2.41%)
elapsed: 20012 us, error: 12 us (0.06%)
timers::precise_sleep::sleep_for
elapsed: 20408 us, error: 408 us (2.04%)
elapsed: 20011 us, error: 11 us (0.06%)
elapsed: 20476 us, error: 476 us (2.38%)
elapsed: 20331 us, error: 331 us (1.65%)
elapsed: 20146 us, error: 146 us (0.73%)
timers::deadline_sleep::sleep_for
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
wait time: 10000 us
std::this_thread::sleep_for
elapsed: 10074 us, error: 74 us (0.74%)
elapsed: 10482 us, error: 482 us (4.82%)
elapsed: 10012 us, error: 12 us (0.12%)
elapsed: 10007 us, error: 7 us (0.07%)
elapsed: 10431 us, error: 431 us (4.31%)
timers::precise_sleep::sleep_for
elapsed: 10429 us, error: 429 us (4.29%)
elapsed: 10157 us, error: 157 us (1.57%)
elapsed: 10010 us, error: 10 us (0.10%)
elapsed: 10253 us, error: 253 us (2.53%)
elapsed: 10490 us, error: 490 us (4.90%)
timers::deadline_sleep::sleep_for
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10001 us, error: 1 us (0.01%)
wait time: 5000 us
std::this_thread::sleep_for
elapsed: 5151 us, error: 151 us (3.02%)
elapsed: 5476 us, error: 476 us (9.52%)
elapsed: 5471 us, error: 471 us (9.42%)
elapsed: 5469 us, error: 469 us (9.38%)
elapsed: 5473 us, error: 473 us (9.46%)
timers::precise_sleep::sleep_for
elapsed: 5017 us, error: 17 us (0.34%)
elapsed: 5476 us, error: 476 us (9.52%)
elapsed: 5487 us, error: 487 us (9.74%)
elapsed: 5444 us, error: 444 us (8.88%)
elapsed: 5009 us, error: 9 us (0.18%)
timers::deadline_sleep::sleep_for
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
wait time: 1000 us
std::this_thread::sleep_for
elapsed: 1013 us, error: 13 us (1.30%)
elapsed: 1010 us, error: 10 us (1.00%)
elapsed: 1486 us, error: 486 us (48.60%)
elapsed: 1459 us, error: 459 us (45.90%)
elapsed: 1014 us, error: 14 us (1.40%)
timers::precise_sleep::sleep_for
elapsed: 1013 us, error: 13 us (1.30%)
elapsed: 1009 us, error: 9 us (0.90%)
elapsed: 1010 us, error: 10 us (1.00%)
elapsed: 1006 us, error: 6 us (0.60%)
elapsed: 1008 us, error: 8 us (0.80%)
timers::deadline_sleep::sleep_for
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
wait time: 500 us
std::this_thread::sleep_for
elapsed: 1306 us, error: 806 us (161.20%)
elapsed: 1467 us, error: 967 us (193.40%)
elapsed: 1472 us, error: 972 us (194.40%)
elapsed: 1471 us, error: 971 us (194.20%)
elapsed: 1476 us, error: 976 us (195.20%)
timers::precise_sleep::sleep_for
elapsed: 515 us, error: 15 us (3.00%)
elapsed: 524 us, error: 24 us (4.80%)
elapsed: 512 us, error: 12 us (2.40%)
elapsed: 516 us, error: 16 us (3.20%)
elapsed: 512 us, error: 12 us (2.40%)
timers::deadline_sleep::sleep_for
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
wait time: 100 us
std::this_thread::sleep_for
elapsed: 1253 us, error: 1153 us (1153.00%)
elapsed: 1464 us, error: 1364 us (1364.00%)
elapsed: 1476 us, error: 1376 us (1376.00%)
elapsed: 1473 us, error: 1373 us (1373.00%)
elapsed: 1465 us, error: 1365 us (1365.00%)
timers::precise_sleep::sleep_for
elapsed: 447 us, error: 347 us (347.00%)
elapsed: 474 us, error: 374 us (374.00%)
elapsed: 467 us, error: 367 us (367.00%)
elapsed: 479 us, error: 379 us (379.00%)
elapsed: 461 us, error: 361 us (361.00%)
timers::deadline_sleep::sleep_for
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
wait time: 1 us
std::this_thread::sleep_for
elapsed: 1309 us, error: 1308 us (130800.00%)
elapsed: 1009 us, error: 1008 us (100800.00%)
elapsed: 1473 us, error: 1472 us (147200.00%)
elapsed: 1481 us, error: 1480 us (148000.00%)
elapsed: 1009 us, error: 1008 us (100800.00%)
timers::precise_sleep::sleep_for
elapsed: 8 us, error: 7 us (700.00%)
elapsed: 500 us, error: 499 us (49900.00%)
elapsed: 487 us, error: 486 us (48600.00%)
elapsed: 483 us, error: 482 us (48200.00%)
elapsed: 497 us, error: 496 us (49600.00%)
timers::deadline_sleep::sleep_for
elapsed: 1 us, error: 0 us (0.00%)
elapsed: 1 us, error: 0 us (0.00%)
elapsed: 1 us, error: 0 us (0.00%)
elapsed: 1 us, error: 0 us (0.00%)
elapsed: 1 us, error: 0 us (0.00%)
wait time: 100 us
std::this_thread::sleep_for
elapsed: 1012 us, error: 912 us (912.00%)
elapsed: 1476 us, error: 1376 us (1376.00%)
elapsed: 1007 us, error: 907 us (907.00%)
elapsed: 1977 us, error: 1877 us (1877.00%)
elapsed: 1477 us, error: 1377 us (1377.00%)
timers::precise_sleep::sleep_for
elapsed: 451 us, error: 351 us (351.00%)
elapsed: 484 us, error: 384 us (384.00%)
elapsed: 472 us, error: 372 us (372.00%)
elapsed: 466 us, error: 366 us (366.00%)
elapsed: 468 us, error: 368 us (368.00%)
timers::deadline_sleep::sleep_for
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
elapsed: 100 us, error: 0 us (0.00%)
wait time: 500 us
std::this_thread::sleep_for
elapsed: 1293 us, error: 793 us (158.60%)
elapsed: 1469 us, error: 969 us (193.80%)
elapsed: 1473 us, error: 973 us (194.60%)
elapsed: 1482 us, error: 982 us (196.40%)
elapsed: 1467 us, error: 967 us (193.40%)
timers::precise_sleep::sleep_for
elapsed: 512 us, error: 12 us (2.40%)
elapsed: 512 us, error: 12 us (2.40%)
elapsed: 514 us, error: 14 us (2.80%)
elapsed: 513 us, error: 13 us (2.60%)
elapsed: 510 us, error: 10 us (2.00%)
timers::deadline_sleep::sleep_for
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
elapsed: 500 us, error: 0 us (0.00%)
wait time: 1000 us
std::this_thread::sleep_for
elapsed: 1273 us, error: 273 us (27.30%)
elapsed: 1475 us, error: 475 us (47.50%)
elapsed: 1478 us, error: 478 us (47.80%)
elapsed: 1469 us, error: 469 us (46.90%)
elapsed: 1491 us, error: 491 us (49.10%)
timers::precise_sleep::sleep_for
elapsed: 1020 us, error: 20 us (2.00%)
elapsed: 1014 us, error: 14 us (1.40%)
elapsed: 1472 us, error: 472 us (47.20%)
elapsed: 1013 us, error: 13 us (1.30%)
elapsed: 1020 us, error: 20 us (2.00%)
timers::deadline_sleep::sleep_for
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
elapsed: 1000 us, error: 0 us (0.00%)
wait time: 5000 us
std::this_thread::sleep_for
elapsed: 5212 us, error: 212 us (4.24%)
elapsed: 5287 us, error: 287 us (5.74%)
elapsed: 5095 us, error: 95 us (1.90%)
elapsed: 5455 us, error: 455 us (9.10%)
elapsed: 5483 us, error: 483 us (9.66%)
timers::precise_sleep::sleep_for
elapsed: 5021 us, error: 21 us (0.42%)
elapsed: 5012 us, error: 12 us (0.24%)
elapsed: 5377 us, error: 377 us (7.54%)
elapsed: 5494 us, error: 494 us (9.88%)
elapsed: 5022 us, error: 22 us (0.44%)
timers::deadline_sleep::sleep_for
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
elapsed: 5000 us, error: 0 us (0.00%)
wait time: 10000 us
std::this_thread::sleep_for
elapsed: 10296 us, error: 296 us (2.96%)
elapsed: 10480 us, error: 480 us (4.80%)
elapsed: 10495 us, error: 495 us (4.95%)
elapsed: 10271 us, error: 271 us (2.71%)
elapsed: 10483 us, error: 483 us (4.83%)
timers::precise_sleep::sleep_for
elapsed: 10041 us, error: 41 us (0.41%)
elapsed: 10440 us, error: 440 us (4.40%)
elapsed: 10445 us, error: 445 us (4.45%)
elapsed: 10474 us, error: 474 us (4.74%)
elapsed: 10494 us, error: 494 us (4.94%)
timers::deadline_sleep::sleep_for
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10000 us, error: 0 us (0.00%)
elapsed: 10001 us, error: 1 us (0.01%)
elapsed: 10000 us, error: 0 us (0.00%)
wait time: 20000 us
std::this_thread::sleep_for
elapsed: 20442 us, error: 442 us (2.21%)
elapsed: 20016 us, error: 16 us (0.08%)
elapsed: 20451 us, error: 451 us (2.25%)
elapsed: 20039 us, error: 39 us (0.19%)
elapsed: 20266 us, error: 266 us (1.33%)
timers::precise_sleep::sleep_for
elapsed: 20011 us, error: 11 us (0.06%)
elapsed: 20331 us, error: 331 us (1.65%)
elapsed: 20511 us, error: 511 us (2.56%)
elapsed: 20257 us, error: 257 us (1.29%)
elapsed: 20507 us, error: 507 us (2.54%)
timers::deadline_sleep::sleep_for
elapsed: 20001 us, error: 1 us (0.01%)
elapsed: 20001 us, error: 1 us (0.01%)
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
elapsed: 20000 us, error: 0 us (0.00%)
wait time: 50000 us
std::this_thread::sleep_for
elapsed: 50111 us, error: 111 us (0.22%)
elapsed: 50504 us, error: 504 us (1.01%)
elapsed: 50262 us, error: 262 us (0.52%)
elapsed: 50513 us, error: 513 us (1.03%)
elapsed: 50110 us, error: 110 us (0.22%)
timers::precise_sleep::sleep_for
elapsed: 50133 us, error: 133 us (0.27%)
elapsed: 50340 us, error: 340 us (0.68%)
elapsed: 50356 us, error: 356 us (0.71%)
elapsed: 50060 us, error: 60 us (0.12%)
elapsed: 50095 us, error: 95 us (0.19%)
timers::deadline_sleep::sleep_for
elapsed: 50004 us, error: 4 us (0.01%)
elapsed: 50003 us, error: 3 us (0.01%)
elapsed: 50003 us, error: 3 us (0.01%)
elapsed: 50001 us, error: 1 us (0.00%)
elapsed: 50001 us, error: 1 us (0.00%)